WASHINGTON – The government is taking what President Obama calls “a long overdue step” to aid veterans with post-traumatic stress disorder, making it easier for them receive to federal benefits.

The changes that Veteran Affairs Secretary Eric Shinseki will announce Monday fulfill “a solemn responsibility to provide our veterans and wounded warriors with the care and benefits they’ve earned when they come home,” Obama said in his weekly radio and online address Saturday.

The new rules will apply not only to veterans of the Iraq and Afghanistan wars, but also those who served in previous conflicts.

No longer will veterans have to prove what caused their illness. Instead, they would have to show that the conditions surrounding the time and place of their service could have contributed to their illness.

“I don’t think our troops on the battlefield should have to take notes to keep for a claims application,” the president said. “And I’ve met enough veterans to know that you don’t have to engage in a firefight to endure the trauma of war.”

Veterans advocates and some lawmakers have argued that it sometimes could be impossible for veterans to find records of a firefight or bomb blast.

They also have contended that the old rules ignored other causes of PTSD, such as fearing a traumatic event even if it doesn’t occur.

“This is a long overdue step,” Obama said. “It’s a step that proves America will always be here for our veterans, just as they’ve been there for us. We won’t let them down. We take care of our own.”

A study last year by the RAND Corp. think tank estimated that nearly 20 percent of returning veterans, or 300,000, have symptoms of PTSD or major depression.

A senior official at the Department of Veterans Affairs said the agency doesn’t expect the number of veterans receiving benefits for PTSD to rise dramatically, as most veterans with legitimate applications for benefits do eventually get claims.